IMO a scope with an angled eyepiece is MUCH more versatile than the straight version - especially in the prone position. I have a Kowa scope that will rotate 360° in it's mount which allows you to have the eyepiece sitting sideways as well. With the scope low to the ground you don't have to get directly behind the scope and it can sit off to the side somewhat. With that setup, you don't have to break your prone position to look through the scope.

Along the same lines, if you are shooting from a bench using the angled scope, you won't have to crawl over the back of the bench to get to the eyepiece.
For what it's worth....

What Highpower said. I use an angled one so I can set it up alongside me and just lean over to look at it. Works great prone, and also when on it's stand and I'm shooting off-hand.

It even works on those effeminate benches that my club makes us shoot from because the bench-resters that make up a majority of the voting membership have forgotten that there's more to shooting than locking your rifle in a vise on a concrete bench and pulling it's trigger while you sit in a lawn chair next to it.